摘要:

AbstractVisual function in monkeys is subserved at the cortical level by a large number of areas defined by their specific physiological properties and connectivity patterns, For most of these cortical fields, a precise index of their degree of anatomical specialization has not yet been defined, although many regional patterns have been described using Nissl or myelin stains. In the present study, an attempt has been made to elucidate the regional characteristics, and to varying degrees boundaries, of several visual cortical areas in the macaque monkey using an antibody to neurofilament protein (SM132). This antibody labels a subset of pyramidal neurons with highly specific regional and laminar distribution patterns in the cerebral cortex. Based on the staining patterns and regional quantitative analysis, as many as 28 cortical fields were reliably identified. Each field had a homogeneous distribution of labeled neurons, except area V1, where increases in layer IVB cell and in Meynert cell counts paralleled the increase in the degree of eccentricity in the visual field representation. Within the occipitotemporal pathway, areas V3 and V4 and fields in the inferior temporal cortex were characterized by a distinct population of neurofilament‐rich neurons in layers II–IIIa, whereas areas located in the parietal cortex and part of the occipitoparietal pathway had a consistent population of large labeled neurons in layer Va. The mediotemporal areas MT and MST displayed a distinct population of densely labeled neurons in layer VI. Quantitative analysis of the laminar distribution of the labeled neurons demonstrated that the visual cortical areas could be grouped in four hierarchical levels based on the ratio of neuron counts between infragranular and supragranular layers, with the first (areas V1, V2, V3, and V3A) and third (temporal and parietal regions) levels characterized by low ratios and the second (areas MT, MST, and V4) and fourth (frontal regions) levels characterized by high to very high ratios. Such density trends may correspond to differential representation of corticocortically (and corticosubcortically) projecting neurons at several functional steps in the integration of the visual stimuli. In this context, it is possible that neurofilament protein is crucial for the unique capacity of certain subsets of neurons to perform the highly precise mapping functions of the monkey visual system. © 1995 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903520202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study was aimed at determining the synaptic circuitry that contributes to the alterations in thalamic function that accompany changes in behavioral states.The somatosensory sector of the thalamic reticular nucleus (RTN) was identified by microelectrode recording in cats and injected withPhaseolus vulgaris‐leucoagglutinin (PHA‐L). The axons of labeled RTN cells gave rise to collaterals within the RTN and continued into the dorsal thalamus where they terminated predominately in the ventral posterior lateral nucleus (VPL). After small injections in the upper limb representation of RTN, most labeled terminations in VPL were confined to its medial part, suggesting the presence of a topographic organization in the projection.Terminations were concentrated in localized, focal aggregations of boutons. Combined electron microscopic immunocytochemistry, using immunogold labeling for γ‐aminobutyric acid (GABA), showed that the PHA‐L labeled boutons were GABA‐positive terminals that ended in symmetrical synapses. Eighty‐two percent of these synapses were on dendrites of relay neurons, 8.5% on dendrites of interneurons, and 9.3% on somata.The terminals of RTN axons form the majority of axon terminals ending in symmetrical synapses in VPL. Their concentration on relay neurons probably underlies the capacity of the RTN projection to reduce background activity of VPL relay neurons in the awake state and to maintain oscillatory behavior of these neurons in drowsiness and early phases of Sleep. © 1995 Wi

ISSN:0092-7317    

DOI:10.1002/cne.903520203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPrevious light microscopic studies have shown that host olfactory neurons are able to grow into a transplanted fetal olfactory bulb, and behavioral studies have shown that animals with transplanted olfactory bulbs recover functional olfactory abilities. We examined the olfactory bulb transplant at the ultrastructural level to determine whether synaptic contacts are reestablished between host olfactory neurons and donor olfactory bulb. Mature rats that, as neonates, had received embryonic olfactory bulb transplants following olfactory bulb removal were studied. An antibody specific for olfactory marker protein was used to identify the primary olfactory neurons; it was bound by a gold‐conjugated secondary antibody for visualization. To preserve the antigenicity of the olfactory marker protein for immunolabeling, Lowicryl K4M hydrophilic resin was used. Synaptic contacts were unmistakable between labeled axons of host olfactory neurons and unlabeled processes within glomerulus‐like areas of the transplanted olfactory bulb. The surrounding neuropil contained other elements similar to those found in normal tissue, including synaptic contacts between unlabeled profiles. We clearly show that the transplanted olfactory bulb exhibits sufficient plasticity to form an array of normal synaptic contacts, including the contacts from host primary olfactory neurons. © 1995 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903520204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAs part of a long‐term study designed to examine the ontogeny of visual memory in monkeys and its underlying neural circuitry, we have examined the subcortical connections of the inferior temporal cortex in infant monkeys and compared them to those previously described in adult monkeys (Webster et al. [1993] J. Comp. Neurol. 335:73–91). Inferior temporal areas TEO and TE were injected with wheat germ agglutinin conjugated to horseradish peroxidase and tritiated amino acids, respectively, or vice versa, in 1‐week‐old (N = 6) and 3–4‐year‐old (N = 6)Macaca mulatta, and the distributions of labeled cells and terminals were examined in subcortical structures. Although the connections of inferior temporal cortex with subcortical structures were found to be similar in infant and adult monkeys, several projections appear to undergo refinement during development. Quantitative analysis showed that (1) whereas the projection from TE to the superior colliculus is consistent (5 of 5 cases) and widespread in infants, it is less reliable (2 of 7 cases) and limited in areal extent in adults; (2) although the projections from TE to nucleus medialis dorsalis and the tail of the caudate are present in infants and adults, they are reduced in adults; and (3) TEO receives input from the dorsal lateral geniculate nucleus in both infants and adults, but the number of cells giving rise to this projection is lower in adults. There was also a suggestion that TE projects to nucleus paracentralis in infants (2 of 5 cases) but not in adults (0 of 7 cases). No differences between infants and adults were apparent in other subcortical connections, including those with the pulvinar, reticular nucleus, claustrum, and putamen. © 1995 W

ISSN:0092-7317    

DOI:10.1002/cne.903520205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTo determine whether the influence of the bed nucleus of the stria terminalis (BST) on cardiovascular function can be localized to specific cytoarchitectural areas within the BST, urethane (1.3 g/kg)‐anesthetized male Sprague‐Dawley rats were probed for cardiovascular reactive sites. Electrical stimuli (50 μa, 50 Hz, and a 0.5 ms pulse duration), delivered through stereotaxically placed glass semimicroelectrodes, were localized to the BST. Sham‐stimulated animals served as controls. Stimulation sites were correlated with cytoarchitecturally distinct areas within the BST, and changes in mean arterial pressure (MAP) were subjected to statistical analysis.Systematically probing the BST for cardiovascular reactive sites showed a correlation between evoked responses and distinct cytoarchitectural areas. Stimulation of the me dial BST produced increases in MAP; stimulation of the lateral aspect of the BST produced decreases in MAP. Both pressor and depressor responses were evoked from the area ventral to the anterior commissure. Pressor responses were elicited from the area immediatley ventral to the anterior commissure, and depressor responses followed stimulation of an area more ventral. All subnuclei showed corroborating cardiovascular responses to 20–30 n1 microinjection of sodium glutamate. Taken together, these data provide substantial evidence to indicate that the BST, particularly at more rostral areas, consists of a medial pressor area, a lateral depressor area, and a ventral area with both pressor and depressor zone. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903520206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe expression and regulation of seven GABAAreceptor subunit gene transcripts were examined in the adult monkey lateral geniculate nucleus. In situ hybridization histochemistry was used to localize mRNAs of the genes encoding monkey‐specifical α1, α2, α4, α5, β1, β2, and γ2 subunits. The highest levels of expression in the nucleus were for α1, β2, and γ2 subunit transcripts. The levels were substantially higher in the magnocellular than in the parvocellular layers. Alpha‐2, α4, α5, and β1 subunit mRNAs were expressed at much lower levels, and magno‐ and parvocellular layers had approximately equal levels of expression.Following 4‐ or 21‐day periods of monocular deprivation induced by intravitreal injections of tetrodotoxin, levels of the α1, α2, α4, α5, β1, and β2 mRNAs were decreased in the deprived geniculate laminae. Adjacent sections hybridized with probes specific for 67‐kDa glutamic acid decarboxylase (GAD) mRNA also showed decreased levels of expression in deprived laminae after the 21‐day deprivation period. Levels of γ2 receptor subunit mRNA were unaffected by monocular deprivation. In our previous studies, a clearly significant downregulation is observed for this subunit transcript in the visual cortex of monkeys deprived for equivalent times. The differential expression and responses to deprivation in the lateral geniculate nucleus suggest region‐specific regulation of GABAAreceptor su

ISSN:0092-7317    

DOI:10.1002/cne.903520207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of prenatal X‐irradiation on the vibrissal cortical barrelfield of the brain of rats exposed to 200 R on the embryonic day 17 was studied morphologically and electrophysiologically. Cytoarchitectural barrels fail to appear in adult rats that have been subjected to this in utero treatment. However, sections cut in a plane tangential to the vibrissal cortex and examined for cytochrome oxidase (CO), a mitochondrial enzyme, contained a matrix of patterned CO activity which, albeit smaller and weaker in intensity, is similar to CO barrels in normal controls. Current source density analysis of cortical field potentials indicated that, as in the normal cortex, the earliest sink following peripheral stimulation appears in association with this high CO activity. These results suggest that the specific vibrissal thalamocortical pathway sets up an excitatory synaptic activity in the cortex of the irradiated animal. Efficacy of this route in eliciting postsynaptic spikes in the cortical output neurons was confirmed by recording extracellular spike responses to vibrissa displacements from layer Vb pyramidal neurons that were then injected intracellularly with horseradish peroxidase for later anatomical identification. © 1995 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903520208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFreshwater crayfish have well‐developed olfactory systems with an array of receptors that project exclusively to areas in the brain that are functionally specialized for the processing of odors. The accessory lobes are large bilateral areas of neuropil that are anatomically associated with the olfactory lobes. The accessory lobes receive no primary afferents and do not contain the endings of motor efferents; thus, their role in olfaction is still obscure. Intracellular dye filling of interneurons in the deutocerebral commissure in the crayfish brain has shown that they end bilaterally in glomeruli in the accessory lobes, have cell somata in a dorsal cluster medial to the olfactory lobes, and have unilateral projections to the deutocerebral commissure neuropil. Each deutocerebral commissure interneuron has only 6 to 15 output glomeruli in each accessory lobe and does not share glomeruli with other deutocerebral commissure interneurons. The deutocerebral commissure interneurons converge with the dorsal giant serotonin neurons in the accessory lobe glomeruli. Deutocerebral commissure interneurons can be separated into classes according to their projections to the protocerebrum, central body, and deutocerebrum. Physiological responses of the deutocerebral commissure interneurons following photic stimulation of the eyes and electrical stimulation of the second antennae lead to the conclusion that the deutocerebral commissure represents an input to the accessory lobes from the protocerebral neuropils and that visual and tactile inputs are included in the processing performed in the accessory lobes. © 1995 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903520209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have previously identified a population of serotonin‐like immunoreactive (5‐HT‐ir) retinal ganglion cells inRana pipiens.In this study, we examined serotonin‐like immunoreactivity (5‐HTLI) in a probable target of those cells, the optic tectum. We observed both 5‐HT‐ir fibers and cell bodies in this structure. 5‐HT‐ir cells were located in the cellular layers of the tectum, layers 2, 4, and 6, and scattered in its superficial layers. 5‐HT‐ir fibers in the tectum displayed a laminated organization and were located in tectal layers 3, 5, 6, 7, and 9. Retrograde labelling experiments showed that 5‐HT‐ir retinal ganglion cells projected to the optic tectum. However, these experiments also demonstrated that serotonergic neurons in the midbrain tegmentum, the nucleus isthmi, and the medulla did so as well. 5‐HT‐ir fibers seen in lamina A of layer 9 were very much reduced in density in animals in which the optic nerve had been lesioned for 3–6 months. Immunoreactive fibers in lamina B of layer 9 were not affected by the lesion.Our results suggest that 5‐HT‐ir fibers in lamina A of layer 9 are mainly of retinal origin, whereas those in lamina B originate from other brain areas. The 5‐HT‐ir tectal cells located in the cellular layers probably contribute the 5‐HT‐ir fibers seen in la

ISSN:0092-7317    

DOI:10.1002/cne.903520210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe formation of ommatidia in the compound eyes and sensilla on the antennae of the honeybee was followed and the development of their sensory neurons was traced using an antiserum against taurine as a marker. Taurine‐like immunoreactivity (Tau‐IR) is expressed in sensory neurons of several modalities, namely visual, olfactory, gustatory, and mechanosensory. Staining intensity is very high in the larva and in the first half of the pupal stage and gradually decreases towards the end of metamorphosis. In the photoreceptor cells of the compound eyes, Tau‐IR can be detected from the fifth larval instar onwards, prior to differentiation of other components of the ommatidium. Already in the midstage larvae, when the antennal primordia of the adult still lie within the peripodial cavity, a few presumably mechanosensory neurons are labelled in the pedicellus of the developing antenna. The majority of the antennal sensory neurons which are located on the flagellum start to exhibit Tau‐IR upon pupation, long before any cuticular specializations such as sensory hairs or plates are detectable. All known types of antennal sensilla were identified and it could be shown that all of them are innervated by Tau‐IR sensory neurons. Thus, taurine immunocytochemistry can be applied as a useful label for developing sensory neurons. Functional implications of taurine during development are discussed. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903520211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY